This invention relates to a printing device capable of exchanging its printing elements such as daisy wheels when printing is executed.
Generally, in word processing device such as electronic typewriters and word processors, a plurality of character sets (key patterns) are alternately used to define a single keyboard to input as many characters as possible through limited number of keys. Inputted character data are sequentially stored in a text memory, which is generally used as an input data storing means, with an identification code data of the used character set (key pattern) which is stored precedingly to the corresponding character data.
FIG. 7(A) shows an example of the input data stored in a text memory 74. In this example, three key patterns KBI, KBII and KBIII are used. Character data A and B are entered through the key pattern KBI, another character data C through the key pattern KBII, and character data .phi. through the key pattern KBIII.
The wheel-element type printing device used for aforementioned kind of word processing device comprises a plurality of daisy wheels corresponding to a plurality of key patterns, and one of the daisy wheels are installed corresponding to the used key pattern when printing is executed.
For example, when a file data in the text memory shown in FIG. 7(A) is printed, the data is sequentially read out of the text memory, the daisy wheel for key pattern KBI is rotated and the characters corresponding to the data are printed, respectively. In the event that an identification code of key pattern KBII is read out of the text memory, printing is interrupted for exchanging the daisy wheels, while a message indicating the exchange of the daisy wheels is displayed. The daisy wheel corresponding to key pattern KBII having been installed and print start key having been depressed, the printing execution is restarted.
As described above, in the conventional printing device, printing is interrupted and message indicating wheel exchange is displayed every time when the identification code for key pattern KBI, KBII, or KBIII, etc. is read out of the text memory. Practically, however, there are a lot of cases where printing can be kept executing without exchanging the daisy wheels; exchange of the daisy wheels makes the printing execution troublesome and takes more time than actually needed. That is, there are lots of characters simultaneously existing in a plurality of key patterns. It is assumed that, for example, alphabetic letters exist both in key patterns KBI and KBII. In this case, when the data shown in FIG. 7(A) is printed, although the characters of A, B, and C can be printed with the daisy wheel corresponding to the key pattern KBI, printing is interrupted after characters A and B have been printed, and the exchange of the daisy wheels is required, which is practically unnecessary.
If an operator is inexperienced, and unnecessary switching between each key pattern is executed, the printing execution becomes troublesome and requires more time than necessary. For example, assume that the operator first inputs characters using the key pattern KBI, switches to KBII to input other characters, switches back to KBI, then switches again to KBII. In this case, the characters inputted by using the key pattern KBI after inputted by using the key pattern KBII may exist in the key pattern KBII. If so, it is unnecessary to switch from the key pattern KBI to the key pattern KBII and back to the key pattern KBI. This switching operations are unnecessary and can be omitted.
On the other hand, there exist the case that characters inputted by using one key pattern are inserted among the characters inputted by using another key pattern when text is edited. For instance, assume that among the sequence of characters inputted by using the key pattern KBII, another sequence of characters inputted by using the key pattern KBI is inserted. In this case, if the inserted characters exist also in the key pattern KBII, the identification code of the key pattern KBI to be stored in the text memory is actually unnecessary. In other words, unnecessary exchanging of the daisy wheels is required in such a occasion.
This kind of exchange makes the printing execution troublesome and it may unnecessarily take much time to execute printing.